LEDs have many advantages such as long life, low power consumption, and high efficiency. In recent times LED-based luminous products have become more and more popular. LED tubes are especially attractive for general illumination due to the above-mentioned advantages. Indeed, LED tubes are a promising potential replacement for traditional fluorescent light tubes. However, there are two major problems which need to be solved. One is their optical performance. Currently, LED arrays are mounted in a tube for generating light. Due to the concentrated light emission of LED chips, the light distribution of an LED tube is not as uniform and comfortable as that of conventional fluorescent tubes. The light from a conventional LED tube can have a “spotty effect” due to the uneven distribution of light throughout the tube. Another problem is thermal management. The heat generated by LED chips needs to be dissipated effectively in order to guarantee the optical performance and the operation life of LED tubes.
FIG. 1 is a schematic drawing showing a prior art commercial LED light tube. The light tube 1 comprises a PCB strip 10 on which LEDs 20 are mounted and which is inserted into a transparent plastic cylinder 30. The cylinder or “shell” 30 is then sealed with end caps 40. Electric power and a ground line are distributed through the electrode pins 45 on the end caps 40. In this typical structure, the LEDs 20 are facing towards the front side 30a of the tube 39, emitting light directly to outside the tube. Since the light emitted from LEDs 20 has a relatively small angle, the distribution of the light is rather non-uniform. This gives rise to a “spotty effect”. The surface of the shell 30 may be roughened or a diffuser may be added to scatter the light. However, such arrangements will substantially reduce the optical output. Furthermore, there is limited thermal management that can be done in the existing commercial LED light tubes due to the simplicity of mechanical structure.